We wish to determine the extent to which the reactions of bisulfite (the aqueous form of sulfur dioxide) with nucleic acids contribute to the biological damage caused by sulfur dioxide. In the coming year, we will pursue the following goals: a) We will continue our studies on the effect of low bisulfite concentrations upon Eschericia coli. The principal targets involved in the observed inhibition of growth, protein, and nucleic acid synthesis, will be measured; b) The rates of deamination by bisulfite of single and double stranded DNA, and of DNA histone complexes by bisulfite will be measured, and compared to the background buffer-catalyzed deamination; c) The mechanism and conditions for free radical cleavage of DNA, induced by bisulfite, will be explored; d) Our observed bisulfite-catalyzed cross-linking of DNA will be characterized thoroughly. The study will be extended to native chromatin.